EP0875987A1 - Frequency synthesiser - Google Patents
Frequency synthesiser Download PDFInfo
- Publication number
- EP0875987A1 EP0875987A1 EP98302819A EP98302819A EP0875987A1 EP 0875987 A1 EP0875987 A1 EP 0875987A1 EP 98302819 A EP98302819 A EP 98302819A EP 98302819 A EP98302819 A EP 98302819A EP 0875987 A1 EP0875987 A1 EP 0875987A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- frequency
- signals
- synthesiser
- phase
- signal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
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- 229920005994 diacetyl cellulose Polymers 0.000 abstract description 9
- 238000001228 spectrum Methods 0.000 description 8
- 238000000034 method Methods 0.000 description 4
- 230000001419 dependent effect Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 239000013598 vector Substances 0.000 description 1
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Classifications
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F1/00—Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00
- G06F1/02—Digital function generators
- G06F1/03—Digital function generators working, at least partly, by table look-up
- G06F1/0321—Waveform generators, i.e. devices for generating periodical functions of time, e.g. direct digital synthesizers
- G06F1/0342—Waveform generators, i.e. devices for generating periodical functions of time, e.g. direct digital synthesizers for generating simultaneously two or more related waveforms, e.g. with different phase angles only
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
- H03B28/00—Generation of oscillations by methods not covered by groups H03B5/00 - H03B27/00, including modification of the waveform to produce sinusoidal oscillations
Definitions
- the present invention relates to a frequency synthesiser and more particularly to a frequency synthesiser utilising a direct digital frequency synthesiser.
- Direct Digital Synthesis is a well established circuit technique used in frequency synthesisers in applications where wide frequency ranges or very fast frequency hopping, or both. are required.
- One such synthesiser using this technique is the SP2002 400 MHz Direct Digital Frequency Synthesiser (DDFS) manufactured by GEC Plessey Semiconductors.
- DDFS Direct Digital Frequency Synthesiser
- GEC Plessey Semiconductors This synthesiser chip is able to produce square, triangular and sinewave in phase and quadrature output signals at a frequency dependent on an applied clock frequency and an applied binary word.
- the levels of spurious signals on the outputs of such frequency synthesisers can be too high for use as, for example, the local oscillator in a radio receiver to be practical.
- phase related spurs are orthogonal to the carrier whilst amplitude related spurs are in-phase or anti-phase with the carrier.
- the magnitude, number and position of the spurs in the output spectrum is related to the ROM look up table size, the non-linearities of the DACs, the amount of phase accumulator truncation and the frequency select commands of a DDFS.
- the in phase and quadrature signals can be represented mathematically as U and V respectively:
- U A o cos (2 ⁇ F o t) + A 1 sin (2 ⁇ t (F o + F 1 )) + A 1 sin (2 ⁇ t (F o - F 1 ))
- V A o sin (2 ⁇ F o t) + A 1 cos (2 ⁇ t (F o + F 1 )) + A 1 cos (2 ⁇ t (F o - F 1 )) where: -
- the largest term of the result is at 2 F o ; i.e. the carrier frequency has been doubled by multiplying the in phase and quadrature signals together.
- the terms with coefficient A 1 2 are small enough to neglect if the DACs are above, say, 6 bits in size.
- the A 1 2 spurs are 96 dB down.
- the terms which were at offsets of ⁇ F 1 have been phased out at the double frequency, 2F o .
- a frequency synthesiser for generating a signal at a desired frequency comprising a direct digital frequency synthesiser operable to provide in phase and quadrature output signals at half said desired frequency; and a balanced mixer arranged to mix said in phase and quadrature signals to provide said desired frequency signal.
- Use of a frequency synthesiser in accordance with the present invention provides a signal having lower levels of spurious signals, in relation to the carrier frequency signal level, than the signals provided by the direct digital frequency synthesiser utilised therein.
- the frequency synthesiser has the balanced mixer and the direct digital frequency synthesiser fabricated as a single integrated circuit. In this way, mass production can be achieved at a lower cost than is possible with discrete components.
- the direct digital frequency synthesiser is operable to provide sinewave in phase and quadrature output signals, thereby providing a sinewave signal at said desired frequency from the balanced mixer.
- This preferred feature makes the frequency synthesiser particularly suitable for local oscillator and other similar applications.
- a frequency synthesiser in accordance with the present invention comprising an SP2002 DDFS labelled generally at 1, and a micromixer circuit 2.
- the DDFS 1 comprises 30 frequency select inputs FS0 - FS29 which, along with an input enable electrode 3, are connected to a number of solid state latches, indicated generally at 4. These latches 4 feed their outputs into the inputs of an accumulator 5 which generates pulses at the frequency dependent on the clock frequency and the selection made by way of frequency select inputs FS0 - FS29.
- phase and quadrature square wave output signals can be generated by output devices 6 with reference to the pulses from the accumulator 5.
- like pulses are used by either sine logic ROM 8 or triangle logic device 9, dependent on the signals applied to a multiplexer 9 by way of electrodes 10 and 11, to provide analogue in phase and quadrature signals at respective outputs of DACs 12 and 13.
- DDFS 1 To generate a 200 MHz sinewave output signal at terminals 14 and 15, DDFS 1 is applied with suitable signals at frequency select inputs FSO to FS29 and electrodes 10 and 11 to cause DAC 12 to generate a 100 MHz in phase sinewave signal and DAC 13 to generate its quadrature signal.
- the micromixer circuit 2 operating in a linear region, provides at output terminals 14 and 15 a signal having spurious signal levels lower, in relation to the carrier frequency signal level, than the spurious signal levels provided by each of DACs 12 and 13.
- the SP2002 DDFS chip when controlled to provide a 127.5 MHz sinewave output signal from a 1024 MHz clock, has in phase and quadrature output signals each having the spectrum shown in Figure 2.
- This output frequency was chosen, as being near to an integer fraction of the clock frequency, to provide particularly strong spurs in the output signal of the DDFS 1.
- the spectrum comprises a strong carrier frequency signal 16 at 127.5 MHz and a range of spurious signals 17, 18, 19 at approximately 4 MHz spacings on each side thereof.
- the largest spur 17 is at -35dBc.
- the corresponding spur 18, on the other side of the carrier frequency is slightly smaller due to the complex mix of phase terms and amplitude terms in the signal.
- Figure 3 shows the spectrum of an output signal provided by a frequency synthesiser in accordance with the present invention.
- FIG. 4 shows, in block diagram form, a second embodiment of a frequency synthesiser in accordance with the present invention.
- a Gilbert cell circuit 22 is fabricated on the same chip as DDFS 1, between the outputs of DACs 12 and 13 and chip output terminals 24 and 25.
- the balanced mixer is implemented as a Gilbert cell circuit 22 because it is more suited to monolithic production than are micromixer circuits.
- This embodiment allows mass production of frequency synthesisers in accordance with the present invention at a lower cost than the Figure 1 embodiment.
Abstract
Description
Claims (5)
- A frequency synthesiser for generating a signal at a desired frequency comprising a direct digital frequency synthesiser operable to provide in phase and quadrature output signals at half said desired frequency; and a balanced mixer arranged to mix said in phase and quadrature signals to provide said desired frequency signal.
- A frequency synthesiser in accordance with Claim I in which the balanced mixer and the direct digital frequency synthesiser are fabricated as a single integrated circuit.
- A frequency synthesiser in accordance with either preceding claim in which the direct digital frequency synthesiser is operable to provide sinewave in phase and quadrature output signals, thereby providing a sinewave signal at said desired frequency from the balanced mixer.
- A frequency synthesiser in accordance with any preceding claim in which the balanced mixer is a Gilbert cell circuit which, in use, operates in a linear region.
- A frequency synthesiser in accordance with any of Claims 1 to 3 in which the balanced mixer is a micromixer circuit which, in use, operates in a linear region.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9708943 | 1997-05-01 | ||
GB9708943A GB2324917B (en) | 1997-05-01 | 1997-05-01 | Frequency synthesiser |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0875987A1 true EP0875987A1 (en) | 1998-11-04 |
EP0875987B1 EP0875987B1 (en) | 2003-06-18 |
Family
ID=10811711
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP98302819A Expired - Lifetime EP0875987B1 (en) | 1997-05-01 | 1998-04-09 | Frequency synthesiser |
Country Status (5)
Country | Link |
---|---|
US (1) | US6060917A (en) |
EP (1) | EP0875987B1 (en) |
JP (1) | JPH10341179A (en) |
DE (1) | DE69815591T2 (en) |
GB (1) | GB2324917B (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR101485078B1 (en) * | 2014-10-02 | 2015-01-22 | 엘아이지넥스원 주식회사 | Apparatus for generating multi frequency signal |
KR101485079B1 (en) * | 2014-10-02 | 2015-01-22 | 엘아이지넥스원 주식회사 | Method for generating multi frequency signal of dds |
Families Citing this family (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6587863B1 (en) * | 2000-06-27 | 2003-07-01 | Analog Devices, Inc. | Multiphase, interleaved direct digital synthesis methods and structures |
US6692708B2 (en) * | 2001-04-05 | 2004-02-17 | Symyx Technologies, Inc. | Parallel reactor for sampling and conducting in situ flow-through reactions and a method of using same |
KR100407693B1 (en) * | 2001-07-05 | 2003-11-28 | 한국전자통신연구원 | ROM division method, and a DDFS using the method |
US6522176B1 (en) * | 2001-11-15 | 2003-02-18 | Itt Manufacturing Enterprises, Inc. | Low spurious direct digital synthesizer |
GB0210602D0 (en) * | 2002-05-09 | 2002-06-19 | Ibm | Circuit and method for use in data compression |
US7023368B1 (en) * | 2004-08-31 | 2006-04-04 | Euvis, Inc. | Digital-to-analog signal converting apparatus and method to extend usable spectrum over Nyquist frequency |
US7706484B2 (en) * | 2006-06-22 | 2010-04-27 | International Business Machines Corporation | Coherent frequency clock generation and spectrum management with non-coherent phase |
CN101542031A (en) * | 2006-09-06 | 2009-09-23 | 陶氏环球技术公司 | Knit fabrics comprising olefin block interpolymers |
US8284822B2 (en) * | 2007-02-27 | 2012-10-09 | Broadcom Corporation | Method and system for utilizing direct digital frequency synthesis to process signals in multi-band applications |
US20100054377A1 (en) * | 2008-08-28 | 2010-03-04 | Honeywell International Inc. | Systems and methods for spurious signal reduction in multi-mode digital navigation receivers |
US8766830B2 (en) * | 2010-04-29 | 2014-07-01 | Agilent Technologies, Inc. | Digital waveform synthesizer for NMR phase control |
CN103196846B (en) * | 2013-03-18 | 2015-01-21 | 山东大学 | Standard signal source of gas absorption state in analog optical fiber gas sensing and detecting |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4454486A (en) * | 1981-11-02 | 1984-06-12 | Hewlett-Packard Company | Waveform synthesis using multiplexed parallel synthesizers |
US5661424A (en) * | 1993-01-27 | 1997-08-26 | Gte Laboratories Incorporated | Frequency hopping synthesizer using dual gate amplifiers |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5077546A (en) * | 1990-11-07 | 1991-12-31 | General Electric Company | Low phase noise frequency multiplier |
JPH05160640A (en) * | 1991-08-14 | 1993-06-25 | Yokogawa Electric Corp | Direct digital synthesizer |
US5304938A (en) * | 1992-11-18 | 1994-04-19 | Gec Plessey Semiconductors, Inc. | Method and apparatus for providing a lower frequency signal with reference to a higher frequency signal |
US5521533A (en) * | 1994-09-16 | 1996-05-28 | Rockwell International | Apparatus and method for spurious signal reduction in direct-digital synthesizers |
-
1997
- 1997-05-01 GB GB9708943A patent/GB2324917B/en not_active Expired - Fee Related
-
1998
- 1998-04-09 DE DE69815591T patent/DE69815591T2/en not_active Expired - Fee Related
- 1998-04-09 EP EP98302819A patent/EP0875987B1/en not_active Expired - Lifetime
- 1998-04-22 US US09/064,276 patent/US6060917A/en not_active Expired - Lifetime
- 1998-04-23 JP JP10128121A patent/JPH10341179A/en active Pending
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4454486A (en) * | 1981-11-02 | 1984-06-12 | Hewlett-Packard Company | Waveform synthesis using multiplexed parallel synthesizers |
US5661424A (en) * | 1993-01-27 | 1997-08-26 | Gte Laboratories Incorporated | Frequency hopping synthesizer using dual gate amplifiers |
Non-Patent Citations (2)
Title |
---|
KISHNER L J ET AL: "AN 800-MHZ MONOLITHIC GAAS HBT SERRODYNE MODULATOR", IEEE JOURNAL OF SOLID-STATE CIRCUITS, vol. 30, no. 10, 1 October 1995 (1995-10-01), pages 1041 - 1050, XP000536364 * |
NICHOLAS H T ET AL: "AN ANALYSIS OF THE OUTPUT SPECTRUM OF DIRECT DIGITAL FREQUENCY SYNTHESIZERS IN THE PRESENCE OF PHASE-ACCUMULATOR TRUNCATION", PROCEEDINGS OF THE 41ST ANNUAL FREQUENCY SYMPOSIUM, 1987, philadelphia, pages 495 - 502, XP000013091 * |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR101485078B1 (en) * | 2014-10-02 | 2015-01-22 | 엘아이지넥스원 주식회사 | Apparatus for generating multi frequency signal |
KR101485079B1 (en) * | 2014-10-02 | 2015-01-22 | 엘아이지넥스원 주식회사 | Method for generating multi frequency signal of dds |
Also Published As
Publication number | Publication date |
---|---|
US6060917A (en) | 2000-05-09 |
GB9708943D0 (en) | 1997-06-25 |
GB2324917A (en) | 1998-11-04 |
JPH10341179A (en) | 1998-12-22 |
GB2324917B (en) | 2001-03-14 |
DE69815591D1 (en) | 2003-07-24 |
EP0875987B1 (en) | 2003-06-18 |
DE69815591T2 (en) | 2003-12-11 |
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